1. Field of the Invention
This invention relates broadly to flexible polymer tubing having braided elements. This invention particularly relates to tubing having braided elements capable of carrying an electrical and/or optical signal.
2. State of the Art
Catheters are generally elongate flexible tubular devices intended to be inserted into body vessels, such as through the vascular system. It is well known to imbed wires in the wall of a catheter in order to impart torsional stiffness and kink resistance to the catheter, and structural rigidity sufficient to maintain an open lumen within the catheter. In addition, particular cardiovascular electrode catheters are used to electrically stimulate and/or monitor the heart, and in some cases, to modify the heart tissue. These catheters are provided with a signal transmitting element, e.g., a conductive element, extending a length of the catheter.
For example, U.S. Pat. No. 5,057,092 to Webster, Jr. discloses a catheter having a polymeric inner wall defining a central lumen for the passage of fluids or a guidewire therethrough, a reinforcing non-conductive braided mesh around the inner wall, and another polymeric outer wall about the braided mesh. Electrodes are provided at the distal end of the catheter, and a plurality of conductive wires extend the length of the catheter, coupled at their distal ends to the electrodes and couplable at their proximal ends to an electrostimulator or recorder. In one embodiment, the uninsulated conductive wires are built into the braided mesh. To prevent a short circuit, Webster, Jr. teaches that the conductive wires must run parallel within the braid, and not cross each other. As such, Webster, Jr. teaches that the conductive wires should be non-insulated and non-overlapping.
U.S. Pat. No. 5,630,806 to Inagaki et al. discloses a catheter having a inner layer defining a lumen, a spiral wound radiopaque reinforcement layer having one or more like spiral wound elements, each of which does not cross itself or overlap another. In one embodiment, the spiral wound elements are uninsulated conductors which permit the reinforcement layer to conduct signals as well as provide reinforcement. However, having the same elements function as both conductors and reinforcements is not particularly desirable as elements which provide the desired conductivity may not provide the desired reinforcement, and elements which provide the desired reinforcement may not provide the desired conductivity.
U.S. Pat. No. 5,591,142 to Van Erp discloses a catheter having a reinforcement braid made exclusively of like electrically conductive wires. The braid is located between two tubular layers of the catheter. The wires of the braid are separately insulated and grouped into at least two bundles which are then woven together, i.e., crisscrossed, about an inner layer of the catheter. Each of the wires of the braid can function as a conductor, and may be color coded to facilitate identifying the proximal and distal ends of particular conductors for coupling to sensor devices. However, such a design is limiting in that electrically conductive wires may not provide the most satisfactory reinforcement for a particular catheter. For example, in some situations, as recognized by U.S. Pat. No. 5,057,092 to Webster, Jr., discussed above, non-conductive braid elements may provide structural advantage for manipulating the catheter.